Sodium aceneuramate is a sodium salt of aceneuramic acid (sialic acid). It is an effective inhalant expectorant. Inhalation of sodium aceneuramate repaired inflammation in the airway, and caused bronchitic rabbits to produce sputa with a low viscosity, similar to normal air-way secretions. Sodium aceneuramate protected the mucociliary transport impaired bycigarette smoke in a dose-dependent manner. The results suggest that sodium aceneuramate may participate in the defense mechanism in the airway against irritant gases. Sodium aceneuramate inhibited bronchial anaphylaxis and the release of histamine into bronchoalveolar lavages. Sodium aceneuramate has an action which elevates the viscoelasticity of secretions in the respiratory tract.